This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. PROJECT B. ARRAY BASED DETECTION OF ANTIGEN SPECIFIC T CELLS. Mark Davis, P.I., Yueh-hsiu Chien, and Patrick Brown and Co-P.l.s. Overview. The ability to detect and quantitate antigen specific T cells in human peripheral blood with the tetrameric peptide/MHC staining reagents have proven to be very useful for following disease progression and for evaluating the efficacy of intervention. However, this technique requires a fluorescent activated cell sorter, which severely limits the throughput, the number of specificities that can be surveyed and the potential for automation. In addition, it requires relatively large quantities of blood, which is a particular problem with samples from young children (as noted in the preceding proposals). To facilitate the analysis of immune responses developed during Influenza virus infection and to analyze the effect of vaccination, we have generated preliminary results showing that the tetramers can be arrayed on glass slides to retain antigen specific T cells and the retained T cells can be detected with fluorescent microscopy. The goal of this application is to expand and refine these results to develop a high throughput, array-based, antigen specific T cell quantitation assay that would allow the assessment of many different T cell specificities with a single blood sample. This should provide a convenient and potentially automated means of surveying multiple samples.